Geochemical Negative Emissions Technologies: Part I. Review

Abstract

Over the previous two decades, a diverse array of geochemical negative emissions technologies (NETs) have been proposed, which use alkaline minerals for removing and permanently storing atmospheric carbon dioxide (CO2). Geochemical NETs include CO2 mineralization (methods which react alkaline minerals with CO2, producing solid carbonate minerals), enhanced weathering (dispersing alkaline minerals in the environment for CO2 drawdown) and ocean alkalinity enhancement (manipulation of ocean chemistry to remove CO2 from air as dissolved inorganic carbon). CO2 mineralization approaches include in situ (CO2 reacts with alkaline minerals in the Earth's subsurface), surficial (high surface area alkaline minerals found at the Earth's surface are reacted with air or CO2-bearing fluids), and ex situ (high surface area alkaline minerals are transported to sites of concentrated CO2 production). Geochemical NETS may also include an approach to direct air capture (DAC) that harnesses surficial mineralization reactions to remove CO2 from air, and produce concentrated CO2. Overall, these technologies are at an early stage of development with just a few subjected to field trials. In Part I of this work we have reviewed the current state of geochemical NETs, highlighting key features (mineral resources; processes; kinetics; storage durability; synergies with other NETs such as DAC, risks; limitations; co-benefits, environmental impacts and life-cycle assessment). The role of organisms and biological mechanisms in enhancing geochemical NETs is also explored. In Part II, a roadmap is presented to help catalyze the research, development, and deployment of geochemical NETs at the gigaton scale over the coming decades.

Biocement from the ocean: Hybrid microbial-electrochemical mineralization of CO2

“…Potential alkaline feedstocks could be abundant natural silicate rocks such as basalts or olivine, or industrial byproducts of steel, aluminum, and cement manufacturing. ( Campbell et al., 2022 ; Renforth, 2019 ). In each of these cases, the decrease in calcium ion concentrations can be overwhelmed by the larger shift in carbonate equilibrium toward HCO 3 − and CO 3 2− such that Ω arag would increase.…”

Geochemical Negative Emissions Technologies: Part II. Roadmap

“…Today, demand for geochemical NETs is generated primarily through voluntary carbon markets and corporate commitments (Battersby et al, 2022). Demand for durable forms of carbon removal has been increasing, with the most significant recent commitment being the $925 million advance market commitment by Frontier (2022). Geochemical NETs offer permanent CO 2 storage and may be competitive applicants for such funding (Joppa et al, 2021).…”

“…This perspective article is based on a comprehensive review on Geochemical NETs, available here: Campbell et al (2022).…”

An Assessment of the Potential Value for Climate Remediation of Ocean Calcifiers in Sequestration of Atmospheric Carbon

“…We calculate that the paradigm shift (from 'shellfish as food' to 'shellfish for carbon sequestration') makes bivalve mollusc farming and microalgal farming enterprises, viable, profitable, and sustainable, alternatives to all industrial carbon capture negative emissions technologies [109] and terrestrial biotechnologies in use or in development today. Aquaculture can be scaled from supporting indigenous subsistence communities [93,104] through to industrial facilities like offshore platforms (re-purposed oil/gas-rigs) and/or factory ships producing nutritious human food/animal feed in massive quantities as a byproduct of their carbon sequestration service [110].…”